Methods and devices for knee surgery with inertial sensors

ABSTRACT

A method of navigating a cutting instrument, via a computer system, the method comprising: (a) mounting a patient-specific anatomical mapper (PAM) to a human in a single known location and orientation, where the PAM includes a surface precisely and correctly mating with a human surface correctly in only a single location and orientation; (b) mounting a reference inertial measurement unit (IMU) to the human; (c) operatively coupling a guide to the PAM, where the guide includes an instrument inertial measurement unit (IMU) and at least one of a cutting slot and a pin orifice; (d) outputting data from the reference IMU and the instrument IMU indicative of changes in position and orientation of the guide with respect to the human; (e) repositioning the guide with respect to the human to a position and an orientation consistent with a plan for carrying out at least one of a cut and pin placement; and, (f) visually displaying feedback concerning the position and orientation of the guide with respect to the human using data output from the reference IMU and the instrument IMU, which data is processed by a computer program and the computer program directs the visually displayed feedback.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/687,462, titled “METHODS AND DEVICES FOR KNEESURGERY WITH INERTIAL SENSORS,” filed Jun. 20, 2018, the disclosure ofwhich is incorporated herein by reference.

INTRODUCTION TO THE INVENTION

The present disclosure is directed to devices, methods, and techniquesrelated to computer aided surgery and computer planned surgery.

Computer aided surgery has been shown to improve precision of orthopedicsurgery in most large joints, specifically hip and knee joints.Conventional knee replacement surgery requires several surgical trayswith a plethora of unique surgical instruments, where each surgical trayis expensive, heavy, and requires sterilization for reuse. Technologyhas been developed in the field of computer aided surgery to reduce thenumber of instruments while maintaining or slightly improving precision.Current configurations of such technologies include surgical robotics,optical navigation, and inertial sensor-based instrumentation.

Each of these current systems has inherent advantages and disadvantages.For example, robotic systems are expensive, bulky, and often requiresignificant time to setup, tear down, and execute the surgicalprocedure. Optical systems are also expensive, suffer from line-of-sightissues, and require similar time as robotics to setup and tear down.Inertial systems, in most of their current forms, require significantmanual instrumentation to constrain the degrees of freedom due toshortcomings in the technology, often requiring at least one or twoinstrument trays. Therefore, there is a need for technology to improvesurgical precision without the cost, space constraints, and capitalequipment requirements of current technologies.

What is disclosed herein are techniques, methods, and devices as part ofa computer aided surgical navigation system for the knee joint surgeriesand instrumentation to support the same so that the navigation systemmay be delivered in a “just-in-time” manner with minimalinstrumentation.

It is a first aspect of the present invention to provide a method ofnavigating a cutting instrument, via a computer system, the methodcomprising: (a) mounting a patient-specific anatomical mapper (PAM) to ahuman in a single known location and orientation, where the PAM includesa surface precisely and correctly mating with a human surface correctlyin only a single location and orientation; (b) mounting a referenceinertial measurement unit (IMU) to the human; (c) operatively coupling aguide to the PAM, where the guide includes an instrument inertialmeasurement unit (IMU) and at least one of a cutting slot and a pinorifice; (d) outputting data from the reference IMU and the instrumentIMU indicative of changes in position and orientation of the guide withrespect to the human; (e) repositioning the guide with respect to thehuman to a position and an orientation consistent with a plan forcarrying out at least one of a cut and pin placement; and, (f) visuallydisplaying feedback concerning the position and orientation of the guidewith respect to the human using data output from the reference IMU andthe instrument IMU, which data is processed by a computer program andthe computer program directs the visually displayed feedback.

In a more detailed embodiment of the first aspect, the PAM is mounted toat least one of a tibia and a femur. In yet another more detailedembodiment, the reference IMU is mounted to at least one of a tibia anda femur. In a further detailed embodiment, operatively coupling theguide to the PAM includes using a mechanical connection comprising atleast two joints to allow repositioning of the cutting guide independentof the PAM. In still a further detailed embodiment, the at least twojoints comprise at least one of a revolute joint and a spherical joint.In a more detailed embodiment, the at least two joints comprise a pairof revolute joints and a spherical joint. In a more detailed embodiment,the method further includes registering the reference IMU with respectto the instrument IMU while at least one of the reference IMU and theinstrument IMU is in a known position and orientation with respect tothe human. In another more detailed embodiment, the instrument IMU ismountable to the guide in only a single known location and orientation.In yet another more detailed embodiment, the reference IMU is mountableto the patient in a plurality of locations and orientations. In stillanother more detailed embodiment, registering the reference IMU withrespect to the instrument IMU includes holding the IMUs stationary withrespect to one another for a predetermined period of time.

In yet another more detailed embodiment of the first aspect,repositioning the guide with respect to the human includes repositioningthe guide with respect to the PAM. In yet another more detailedembodiment, the method further includes performing an evaluation using aload measuring device operatively coupled to the instrument IMU toassess knee joint laxity. In a further detailed embodiment, the plancomprises a plan for placing the pin. In still a further detailedembodiment, visually displaying feedback includes displaying a virtualmodel of patient anatomy and reference indicia reflecting a position ofthe guide with respect to the patient anatomy. In a more detailedembodiment, visually displaying feedback includes displaying a virtualmodel of patient anatomy and reference indicia reflecting an intendedlocation for the cut on the virtual model. In a more detailedembodiment, the method further includes mounting at least one pin to aresected aspect of the patient, orienting a static cutting guide withrespect to the patient using the at least one pin, and mounting thestatic cutting guide to the patient post orienting the static cuttingguide. In another more detailed embodiment, the method further includesmounting at least one pin to a resected aspect of the patient, orientinga guide foot with respect to the patient using the at least one pin,mounting the guide foot to the patient post orienting the guide foot,discontinuing the operative coupling between the PAM and guide, andoperatively coupling the guide to the guide foot.

It is a second aspect of the present invention to provide a surgicalequipment system comprising: (a) a first inertial measurement unit (IMU)having a gyroscope, an accelerometer, and a magnetometer; (b) a secondinertial measurement unit (IMU) having a gyroscope, an accelerometer,and a magnetometer, the second IMU configured to be mounted to areference device, where the reference device is configured to be mountedto patient anatomy; (c) a patient-specific anatomical mapper (PAM) thatincludes a surface precisely and correctly mating with a patient anatomysurface in only a single location and orientation, where the PAM isconfigured to be mounted to the patient anatomy surface; and, (d) aguide configured to be operatively coupled to the PAM when in use, theguide including at least one of a cutting slot and a pin orifice, theguide configured to couple to the first IMU in a predetermined knownposition and orientation.

In a more detailed embodiment of the second aspect, the system furtherincludes a controller including software having preloaded at least onevirtual anatomical model of the patient anatomy and a pre-operativesurgical plan indicating the position and orientation of an intendedbone resection with respect to the at least one virtual anatomical modelof the patient anatomy, the controller configured to be communicativelycoupled to the first and second IMUs to receive IMU data and totranslate the received IMU data to determine the position andorientation of the guide with respect to the patient anatomy and outputinstructions for a display to visually represent the virtual anatomicalmodel of the patient anatomy and provide guidance as to whether theguide is positioned with respect to the patient anatomy consistent withthe pre-operative surgical plan to achieve the intended bone resection.In yet another more detailed embodiment, the patient-specific anatomicalmapper is configured to engage at least one of a proximal tibia and adistal femur. In a further detailed embodiment, the patient-specificanatomical mapper comprises a first tibia PAM and a second femur PAM. Instill a further detailed embodiment, the system further includes amechanical connection operative to couple the guide to the PAM, themechanical connection including at least one joint. In a more detailedembodiment, the at least one joint comprises at least two joints. In amore detailed embodiment, the at least two joints include a revolutejoint and a spherical joint. In another more detailed embodiment, the atleast two joints include a pair of revolute joints. In yet another moredetailed embodiment, the mechanical connection is configured toconcurrently mount to a first predetermined location of the PAM and asecond predetermined location of the guide to assume a registrationposition and orientation. In still another more detailed embodiment, thesystem further includes a load measuring device configured to couple tothe first IMU in a known position and orientation.

In yet another more detailed embodiment of the second aspect, the loadmeasuring device comprises at least one of a plurality of piezoresistivesensors, a plurality of capacitive sensors, and a plurality ofpiezoelectric based strain sensors. In yet another more detailedembodiment, the system further comprises an orthopedic implant placementdevice configured to couple to the first IMU in a known position andorientation. In a further detailed embodiment, the orthopedic implantplacement device is configured to couple to an orthopedic implant in apredetermined location and orientation, where the orthopedic implantcomprises at least one of an orthopedic trial and a final orthopedicimplant. In still a further detailed embodiment, the orthopedic implantcomprises at least one of a tibial implant and a femoral implant as partof at least one of a knee replacement surgery or a knee revisionsurgery. In a more detailed embodiment, the system further includes adisplay communicatively coupled to the controller, the display operativeto visually represent the virtual anatomical model of the patientanatomy and provide guidance as to whether the guide is positioned withrespect to the patient anatomy consistent with the pre-operativesurgical plan to achieve the intended bone resection. In a more detailedembodiment, the display comprises a plurality of display windows. Inanother more detailed embodiment, each of the plurality of displaywindows is associated with a stand-alone screen. In yet another moredetailed embodiment, the system further comprises an orthopedic implantcomprising at least one of a final orthopedic implant and an orthopedictrial. In still another more detailed embodiment, the final orthopedicimplant comprises a component of a total knee joint replacement or apartial knee joint replacement.

In a more detailed embodiment of the second aspect, the final orthopedicimplant comprises at least one of a patient-specific femoral componentand a patient-specific tibial component of a total knee replacement. Inyet another more detailed embodiment, the system further includes aguide foot configured to be operatively coupled to the guide when theguide foot is mounted to the patient anatomy in order to facilitate atleast one bone cut.

It is a third aspect of the present invention to provide a method ofusing inertial measurement units to facilitate three dimensionaltracking of a surgical tool, via a computer system, the methodcomprising: (a) mounting a first inertial measurement unit (IMU) to afirst mammalian tissue so that the first IMU is not repositionable withrespect to the first mammalian tissue; (b) operatively coupling a secondinertial measurement unit (IMU) to the first mammalian tissue by using apatient-specific anatomical mapper (PAM) having a surface precisely andcorrectly mating with a surface of the first mammalian tissue in only asingle location and orientation, the second IMU being repositionablewith respect to the first mammalian tissue; (c) registering the positionand orientation of the second IMU with respect to the first mammaliantissue and the first IMU while the PAM is mounted to the first mammaliantissue; (d) mounting the second IMU to a surgical tool; and, (e)tracking a position and an orientation of the surgical tool and firstmammalian tissue in three dimensions while the second IMU is mounted tothe surgical tool and repositionably coupled to the PAM.

In a more detailed embodiment of the third aspect, the method furthercomprises visually displaying feedback concerning the position andorientation of the surgical tool with respect to the first mammaliantissue using data output from the first and second IMUs, which data isprocessed by a computer program and the computer program directs thevisually displayed feedback. In yet another more detailed embodiment,the feedback comprises a virtual model of the first mammalian tissue andfirst indicia on the virtual model indicating the relative real-worldposition of the surgical tool with respect to the first mammaliantissue. In a further detailed embodiment, the feedback further comprisesa second indicia on the virtual model indicating an intended position ofthe surgical tool with respect to the first mammalian tissue consistentwith a predetermined plan. In still a further detailed embodiment, thePAM is mounted to at least one of a tibia and a femur. In a moredetailed embodiment, the first mammalian tissue comprises at least oneof a tibia and a femur. In a more detailed embodiment, the surgical toolis operatively coupled to the PAM. In another more detailed embodiment,operatively coupling the surgical tool to the PAM includes using amechanical connection comprising at least two joints to allowrepositioning of the surgical tool independent of the PAM. In yetanother more detailed embodiment, the at least two joints comprise atleast one of a revolute joint and a spherical joint. In still anothermore detailed embodiment, the at least two joints comprise a pair ofrevolute joints and a spherical joint.

In yet another more detailed embodiment of the third aspect, the secondIMU is mountable to the surgical tool in only a single known locationand orientation. In yet another more detailed embodiment, the first IMUis mountable to the first mammalian tissue in a plurality of locationsand orientations. In a further detailed embodiment, the position andorientation of the second IMU with respect to the first mammalian tissueincludes holding the first and second IMUs stationary with respect toone another for a predetermined period of time. In still a furtherdetailed embodiment, the method further includes performing anevaluation using a load measuring device operatively coupled to thesecond IMU to assess knee joint laxity.

It is a fourth aspect of the present invention to provide a surgicalequipment kit for a knee replacement or revision procedure comprising:(a) a first inertial measurement unit (IMU) having a gyroscope, anaccelerometer, and a magnetometer; (b) a second inertial measurementunit (IMU) having a gyroscope, an accelerometer, and a magnetometer; (c)a tibial patient-specific anatomical mapper (PAM) that includes asurface precisely and correctly mating with a tibial surface in only asingle location and orientation, where the tibial PAM is configured tobe mounted to the tibial surface; and, (d) a femoral patient-specificanatomical mapper (PAM) that includes a surface precisely and correctlymating with a femoral surface in only a single location and orientation,where the femoral PAM is configured to be mounted to the femoralsurface, where the second IMU is configured to be operatively coupled toat least one of the tibial PAM and the femoral PAM.

In a more detailed embodiment of the fourth aspect, the kit furtherincludes a cutting guide configured to be repositionably coupled to atleast one of the tibial PAM and the femoral PAM, the cutting guideincluding at least one of a cutting slot and a pin orifice, the guideconfigured to couple to the first IMU in a predetermined known positionand orientation. In yet another more detailed embodiment, the kitfurther includes a mechanical connection comprising at least two jointsto operatively couple the cutting guide to at least one of the tibialPAM and the femoral PAM. In a further detailed embodiment, theorthopedic implant comprises a non-patient-specific implant. In still afurther detailed embodiment, the non-patient-specific implant includes afemoral condyle and a tibial tray insert. In a more detailed embodiment,the non-patient-specific implant includes a femoral implant having apair of condyles and a tibial tray insert having a pair of condylereceivers. In a more detailed embodiment, the kit further includes areference housing configured to be rigidly mounted to at least one of atibia and a femur, the reference housing configured to mount to thefirst IMU correctly in only a single position and orientation. Inanother more detailed embodiment, the kit further includes a 4-in-1static cutting block. In yet another more detailed embodiment, the kitfurther includes a 4-in-1 reconfigurable cutting block. In still anothermore detailed embodiment, the kit further includes a physical memorydevice upon which is stored computer readable code that, when executedby a computer, is operative to provide surgical navigation guidanceconsistent with a pre-operative plan.

In yet another more detailed embodiment of the fourth aspect, the masscustomized implant includes a femoral implant having a pair of condylesand a tibial tray insert having a pair of condyle receivers. In yetanother more detailed embodiment, the at least two joints comprise atleast one of a revolute joint and a spherical joint. In a furtherdetailed embodiment, the at least two joints comprise a pair of revolutejoints and a spherical joint. In still a further detailed embodiment,the kit further includes an orthopedic implant configured to replace atleast a portion of a knee joint. In a more detailed embodiment, theorthopedic implant comprises a patient-specific implant. In a moredetailed embodiment, the patient-specific implant includes a femoralcondyle and a tibial tray insert. In another more detailed embodiment,the patient-specific implant includes a femoral implant having a pair ofcondyles and a tibial tray insert having a pair of condyle receivers. Inyet another more detailed embodiment, the orthopedic implant comprises amass customized implant. In still another more detailed embodiment, themass customized implant includes a femoral condyle and a tibial trayinsert. In yet another more detailed embodiment, the kit includes a copyof an internet address that may be accessed to provide stored computerreadable code that, when executed by a computer, is operative to providesurgical navigation guidance consistent with a pre-operative plan.

It is a fifth aspect of the present invention to provide a surgicalequipment kit for a knee replacement or revision procedure comprising:(a) a tibial patient-specific anatomical mapper (PAM) that includes asurface precisely and correctly mating with a tibial surface in only asingle location and orientation, where the tibial PAM is configured tobe mounted to the tibial surface; and, (b) a femoral patient-specificanatomical mapper (PAM) that includes a surface precisely and correctlymating with a femoral surface in only a single location and orientation,where the femoral PAM is configured to be mounted to the femoralsurface.

In a more detailed embodiment of the fifth aspect, the kit furtherincludes a first inertial measurement unit (IMU) having a gyroscope, anaccelerometer, and a magnetometer, a second inertial measurement unit(IMU) having a gyroscope, an accelerometer, and a magnetometer, wherethe second IMU is configured to be operatively coupled to at least oneof the tibial PAM and the femoral PAM. In yet another more detailedembodiment, the kit further includes a cutting guide configured to berepositionably coupled to at least one of the tibial PAM and the femoralPAM, the cutting guide including at least one of a cutting slot and apin orifice, the guide configured to couple to the first IMU in apredetermined known position and orientation. In a further detailedembodiment, the kit further includes a mechanical connection comprisingat least two joints to operatively couple the cutting guide to at leastone of the tibial PAM and the femoral PAM. In still a further detailedembodiment, the at least two joints comprise at least one of a revolutejoint and a spherical joint. In a more detailed embodiment, the at leasttwo joints comprise a pair of revolute joints and a spherical joint. Ina more detailed embodiment, the kit further includes an orthopedicimplant configured to replace at least a portion of a knee joint. Inanother more detailed embodiment, the orthopedic implant comprises apatient-specific implant.

In a more detailed embodiment of the fifth aspect, the patient-specificimplant includes a femoral condyle and a tibial tray insert. In yetanother more detailed embodiment, the patient-specific implant includesa femoral implant having a pair of condyles and a tibial tray inserthaving a pair of condyle receivers. In a further detailed embodiment,the orthopedic implant comprises a mass customized implant. In still afurther detailed embodiment, the mass customized implant includes afemoral condyle and a tibial tray insert. In a more detailed embodiment,the mass customized implant includes a femoral implant having a pair ofcondyles and a tibial tray insert having a pair of condyle receivers. Ina more detailed embodiment, the orthopedic implant comprises anon-patient-specific implant. In another more detailed embodiment, thenon-patient-specific implant includes a femoral condyle and a tibialtray insert. In yet another more detailed embodiment, thenon-patient-specific implant includes a femoral implant having a pair ofcondyles and a tibial tray insert having a pair of condyle receivers. Instill another more detailed embodiment, the kit further includes areference housing configured to be rigidly mounted to at least one of atibia and a femur, the reference housing configured to mount to thefirst IMU correctly in only a single position and orientation.

In yet another more detailed embodiment of the fifth aspect, the kitfurther includes a 4-in-1 static cutting block. In yet another moredetailed embodiment, the kit further includes a 4-in-1 reconfigurablecutting block. In a further detailed embodiment, the kit furtherincludes a physical memory device upon which is stored computer readablecode that, when executed by a computer, is operative to provide surgicalnavigation guidance consistent with a pre-operative plan. In still afurther detailed embodiment, the kit further includes a copy of aninternet address that may be accessed to provide stored computerreadable code that, when executed by a computer, is operative to providesurgical navigation guidance consistent with a pre-operative plan. In amore detailed embodiment, the kit further includes a load measuringdevice configured to couple to the first IMU in a known position andorientation. In a more detailed embodiment, the load measuring devicecomprises at least one of a plurality of piezoresistive sensors, aplurality of capacitive sensors, and a plurality of piezoelectric basedstrain sensors. In another more detailed embodiment, the kit furtherincludes an orthopedic implant placement device configured to couple tothe second IMU in a known position and orientation. In yet another moredetailed embodiment, the orthopedic implant placement device isconfigured to correctly couple to an orthopedic implant in only apredetermined location and orientation.

It is a sixth aspect of the present invention to provide a surgicalnavigation system comprising: (a) a tibial patient-specific anatomicalmapper (PAM) that includes a surface precisely and correctly mating witha tibial surface in only a single location and orientation, where thetibial PAM is configured to be mounted to the tibial surface; (b) afemoral patient-specific anatomical mapper (PAM) that includes a surfaceprecisely and correctly mating with a femoral surface in only a singlelocation and orientation, where the femoral PAM is configured to bemounted to the femoral surface; (c) a first inertial measurement unit(IMU) having a gyroscope, a plurality of accelerometers, and amagnetometer; (d) a first transmitter communicatively coupled to thefirst IMU; (e) a second inertial measurement unit (IMU) having agyroscope, a plurality of accelerometers, and a magnetometer; (f) asecond transmitter communicatively coupled to the second IMU; (g) afirst signal receiver communicatively coupled to the first and secondtransmitters; (h) a cutting guide configured to be operatively coupledto at least one of the tibial PAM and the femoral PAM, the guideincluding at least one of a cutting slot and a pin orifice, the cuttingguide configured to couple to the first IMU correctly in only a singleposition and orientation; and, (i) a controller communicatively coupledto the first signal receiver, the controller including software havingaccess to a virtual model of patient anatomy and a pre-operativesurgical plan indicating intended resection cuts with respect to thevirtual model.

In a more detailed embodiment of the sixth aspect, the system furtherincludes a visual display communicatively coupled to the controller,wherein the controller software configured to process data from thefirst and second IMUs to determine the position and orientation of thecutting guide with respect to the patient anatomy and outputinstructions for the visual display to visually represent the virtualmodel of the patient anatomy and provide guidance as to whether thecutting guide is positioned with respect to the patient anatomyconsistent with the pre-operative surgical plan to achieve the intendedresection cuts. In yet another more detailed embodiment, the tibial PAMis configured to engage a proximal portion of a tibia and the femoralPAM is configured to engage a distal portion of the femur. In a furtherdetailed embodiment, the system further includes a mechanical connectionoperative to couple the cutting guide to at least one of the tibial PAMand the femoral PAM, the mechanical connection including at least onejoint. In still a further detailed embodiment, the at least one jointcomprises at least two joints. In a more detailed embodiment, the atleast two joints include a revolute joint and a spherical joint. In amore detailed embodiment, the at least two joints include a pair ofrevolute joints. In another more detailed embodiment, the mechanicalconnection is configured to concurrently mount to a first predeterminedlocation of at least one of the tibial PAM and the femoral PAM and asecond predetermined location of the cutting guide to assume aregistration position and orientation.

In a more detailed embodiment of the sixth aspect, the system furtherincludes a load measuring device configured to couple to the first IMUin a known position and orientation. In yet another more detailedembodiment, the load measuring device comprises at least one of aplurality of piezoresistive sensors, a plurality of capacitive sensors,and a plurality of piezoelectric based strain sensors. In a furtherdetailed embodiment, the system further includes an orthopedic implantplacement device configured to couple to the first IMU in a knownposition and orientation. In still a further detailed embodiment, theorthopedic implant placement device is configured to couple to anorthopedic implant in a predetermined location and orientation, wherethe orthopedic implant comprises at least one of an orthopedic trial anda final orthopedic implant. In a more detailed embodiment, theorthopedic implant comprises at least one of a tibial implant and afemoral implant as part of at least one of a knee replacement surgery ora knee revision surgery. In a more detailed embodiment, the visualdisplay comprises a plurality of display windows. In another moredetailed embodiment, each of the plurality of display windows isassociated with a stand-alone screen. In yet another more detailedembodiment, the system further includes an orthopedic implant comprisingat least one of a final orthopedic implant and an orthopedic trial. Instill another more detailed embodiment, the final orthopedic implantcomprises a component of a total knee joint replacement or a partialknee joint replacement. In yet another more detailed embodiment, thefinal orthopedic implant comprises at least one of a patient-specificfemoral component and a patient-specific tibial component of a totalknee replacement. In yet another more detailed embodiment, the systemfurther includes a guide foot configured to be operatively coupled tothe cutting guide when the guide foot is mounted to the patient anatomyin order to facilitate at least one bone cut.

It is a seventh aspect of the present invention to provide a method ofconducting a surgical procedure, the surgical procedure comprisingrepositioning a cutting guide using navigation guidance displayed on avisual display, the cutting guide including a first inertial measurementunit (IMU), the cutting guide operatively coupled to a femoralpatient-specific anatomical mapper (PAM) that includes a surfaceprecisely and correctly mating with a femoral surface in only a singlelocation and orientation, where the navigation guidance includes atleast one of a virtual model of the cutting guide and a virtual model ofa patient femur, as well as an indication regarding a three dimensionalposition of the cutting guide with respect to the patient femur usingdata from the first IMU, where the navigation guidance also includesguidance for repositioning the cutting guide to make a femoral bone cutconsistent with a pre-operative surgical plan

In a more detailed embodiment of the seventh aspect, the method furtherincludes repositioning the cutting guide using navigation guidancedisplayed on the visual display, the cutting guide including the firstinertial measurement unit (IMU), the cutting guide operatively coupledto a tibial patient-specific anatomical mapper (PAM) that includes asurface precisely and correctly mating with a tibial surface in only asingle location and orientation, where the navigation guidance includesat least one of the virtual model of the cutting guide and a virtualmodel of a patient tibia, as well as an indication regarding the threedimensional position of the cutting guide with respect to the patienttibia using data from the first IMU, where the navigation guidance alsoincludes guidance for repositioning the cutting guide to make a tibialbone cut consistent with the pre-operative surgical plan. In yet anothermore detailed embodiment, the method further includes mounting thefemoral PAM surface to the patient femoral surface in the correct singlelocation and orientation, coupling a second inertial measurement unit(IMU) to the patient femur, and registering the first and second IMUswith respect to one another. In a further detailed embodiment, themethod further includes mounting the tibial PAM surface to the patienttibial surface in the correct single location and orientation, couplinga second inertial measurement unit (IMU) to the patient tibia, andregistering the first and second IMUs with respect to one another. Instill a further detailed embodiment, the navigation guidance includesonly the virtual model of the cutting guide. In a more detailedembodiment, the navigation guidance includes only the virtual model ofthe patient femur. In a more detailed embodiment, the navigationguidance includes at least one of the virtual model of the patient femurand the virtual model of the patient tibia, in addition to a firstcutting line representing the real-world position of the cutting guideand a second cutting line representing an intended pre-operative planposition of the cutting guide for making at least one of the femoralbone cut and the tibial bone cut.

In a further detailed embodiment, the method further includes making thefemoral bone cut using a surgical saw guided by the cutting guide, andrepositioning the cutting guide using navigation guidance displayed onthe visual display, the cutting guide including the first inertialmeasurement unit (IMU) and being operatively coupled to the femoralpatient-specific anatomical mapper (PAM), where the navigation guidanceincludes at least one of the virtual model of the cutting guide and thevirtual model of the patient femur, as well as an indication regardingthe three dimensional position of the cutting guide with respect to thepatient femur using data from the first IMU, where the navigationguidance also includes guidance for repositioning the cutting guide tomake a subsequent femoral bone cut consistent with the pre-operativesurgical plan. In still a further detailed embodiment, the methodfurther includes making the femoral bone cut using a surgical saw guidedby the cutting guide, where the femoral bone cut is a distal resection,and repositioning the cutting guide using navigation guidance displayedon the visual display, the cutting guide including the first inertialmeasurement unit (IMU) and being operatively coupled to the femoralpatient-specific anatomical mapper (PAM), where the navigation guidanceincludes at least one of the virtual model of the cutting guide and thevirtual model of the patient femur, as well as an indication regardingthe three dimensional position of the cutting guide with respect to thepatient femur using data from the first IMU, where the navigationguidance also includes guidance for repositioning the cutting guide todrill holes into the resected femur consistent with the pre-operativesurgical plan. In a more detailed embodiment, the method furtherincludes drilling holes into the resected femur femoral bone using asurgical drill guided by the cutting guide, inserting surgical pins intothe drill holes, repositioning a 4-in-1 cutting guide against theresected femur using the inserted surgical pins for alignment, andmaking at least one femoral resection cut using guidance from the 4-in-1cutting guide. In a more detailed embodiment, the method furtherincludes drilling holes into the resected femur femoral bone using asurgical drill guided by the cutting guide, inserting surgical pins intothe drill holes, repositioning a fixed position cutting guide againstthe resected femur using the inserted surgical pins for alignment, andmaking at least one femoral resection cut using guidance from the fixedposition cutting guide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram depicting portions of an exemplary image guidedsurgical system in accordance with the instant disclosure.

FIG. 2 is a diagram depicting an overview of an exemplary sequence inaccordance with the instant disclosure where pre-operative images areeventually converted into surgical kits and surgical guidanceinstructions.

FIG. 3 is an elevated perspective view of a distal femur showingexemplary components of the image guided surgical system mountedthereto.

FIG. 4 is an elevated perspective view of a distal femur showingexemplary and alternate exemplary components of the image guidedsurgical system mounted thereto.

FIG. 5 is a series of illustrations correlating trigonometry with thepossible locations of a distal femoral resection plane.

FIG. 6 is an end view of a distal femur showing an exemplary patientanatomical mapper mounted thereto, as well as identifying the dimensionthat is medial-lateral, as well as the dimension that isanterior-posterior.

FIG. 7 is a graphical illustration of several different patientanatomical surfaces from a distal femur taken across a population withinan anatomical statistical atlas and how using a generic model, the modelcan be deformed to be patient-specific when creating a patientanatomical mapper.

FIG. 8 are profile and overhead views of the same exemplary cuttingguide and mechanical connection in accordance with the instantdisclosure.

FIG. 9 are frontal and overhead views of the same alternate exemplarycutting guide and mechanical connection in accordance with the instantdisclosure.

FIG. 10 is an overhead view of a further alternate exemplary cuttingguide in accordance with the instant disclosure.

FIG. 11 is an overhead view of an exemplary pin guide and mechanicalconnection in accordance with the instant disclosure.

FIG. 12 is a compilation of graphics reflecting how automatic landmarkswithin a statistical atlas may be identified.

FIG. 13 is a distal end view of three superimposed femurs showing thedifferences in medio-lateral width of the distal resection for a totalknee arthroplasty procedure.

FIG. 14 comprises a series of distal end view of femurs from astatistical atlas showing how much bone is removed for a distalresection cut for different sized femurs.

FIG. 15 is superimposed planar view showing how changes in resectiondepth at the distal end of the femur result in progressively more bonebeing removed.

FIG. 16 is a statistical distribution across a statistical atlaspopulation showing how medio-lateral resection width varies across thepopulation.

FIG. 17 is a distal femur showing an exemplary cutting guiderepositionable among three positions, where a plurality of furtherpositions are possible, and showing how the position of the cuttingguide can be changed by pivoting about a lower revolute joint.

FIG. 18 is a screen shot from a display in accordance with the instantsystem and disclosure showing a virtual distal femur model and a dottedline showing the pre-operative intended location of the resection withrespect to the model.

FIG. 19 is a distal femur showing an exemplary cutting guiderepositionable among a plurality of positions, where a plurality offurther positions are possible, and showing how the position of thecutting guide can be changed by repositioning an upper spherical joint.

FIG. 20 is a screen shot from a display in accordance with the instantsystem and disclosure showing a virtual distal femur model and a firstdotted line showing the pre-operative intended location of the resectionwith respect to the model, as well as a second dotted line showing theactual position of the cutting guide slot with respect to the patientanatomy.

FIG. 21 is an elevated perspective view from the distal end of a femurwith components in accordance with the instant disclosure mountedthereto and points of reference for mathematical calculations inaccordance with the instant disclosure.

FIG. 22 is a side view of a femur with components in accordance with theinstant disclosure mounted thereto and points of reference formathematical calculations in accordance with the instant disclosure,specific to a lower joint.

FIG. 23 is a side view of a femur with components in accordance with theinstant disclosure mounted thereto and points of reference formathematical calculations in accordance with the instant disclosure,specific to an upper joint.

FIG. 24 is an elevated perspective view of a femur with components inaccordance with the instant disclosure mounted thereto and points ofreference for mathematical calculations in accordance with the instantdisclosure, specific to an upper spherical joint.

FIG. 25 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and being used to guide a surgical saw as part of making adistal femoral resection cut.

FIG. 26 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto after making the distal femoral resection cut.

FIG. 27 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and having the cutting guide repositioned in anticipation ofsurgical pin placement into the resected femur after making the distalfemoral resection cut.

FIG. 28 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto, after making the distal femoral resection cut, in anticipationof surgical pin placement into the resected femur.

FIG. 29 is a screen shot from a display in accordance with the instantsystem and disclosure showing a first virtual distal femur model and afirst dotted line showing the pre-operative intended location of theresection with respect to the model, as well as a second dotted lineshowing the actual position of the cutting guide slot with respect tothe patient anatomy (for both the anterior cut and the posterior cut),as well as a second virtual model from a profile view showing the distalresection and areas of the femur yet to be resected.

FIG. 30 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and having a 4-in-1 cutting guide to be mounted to the resectedfemur using pins installed as depicted in FIG. 28.

FIG. 31 is a profile view of a distal end of a femur post making fiveresection cuts in accordance with a TKA pre-operative plan.

FIG. 32 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure dismountedtherefrom.

FIG. 33 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto, including a guide foot that replaces the PAM.

FIG. 34 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and being used to guide a surgical saw as part of making ananterior femoral resection cut.

FIG. 35 is a screen shot from a display in accordance with the instantsystem and disclosure showing a first virtual distal femur model and afirst dotted line showing the pre-operative intended location of theanterior resection with respect to the model, as well as a second dottedline showing the actual position of the cutting guide slot with respectto the patient anatomy.

FIG. 36 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and being used to guide a surgical saw as part of making aposterior femoral resection cut.

FIG. 37 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and being used to guide a surgical saw as part of making ananterior chamfer femoral resection cut.

FIG. 38 is an elevated perspective view of a distal end of the femurshowing components in accordance with the instant disclosure mountedthereto and being used to guide a surgical saw as part of making aposterior chamfer femoral resection cut.

FIG. 39 is a frontal view of a proximal end of the tibia showingcomponents in accordance with the instant disclosure mounted thereto andhaving the cutting guide repositioned in anticipation of making theproximal tibial resection cut.

FIG. 40 is an elevated perspective view of the tibia and components ofFIG. 39.

FIG. 41 is an elevated perspective view of an exemplary placementdevice, mounted to a tibial trial, in accordance with the instantdisclosure.

FIG. 42 is an elevated perspective view of a load measurement device inaccordance with the instant disclosure.

FIG. 43 is a diagram depicting exemplary components that may comprise asurgical kit in accordance with the instant disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The exemplary embodiments of the present disclosure are described andillustrated below to encompass exemplary devices, methods, andtechniques related to computer aided surgery and computer plannedsurgery. Of course, it will be apparent to those of ordinary skill inthe art that the embodiments discussed below are exemplary in nature andmay be reconfigured without departing from the scope and spirit of thepresent invention. However, for clarity and precision, the exemplaryembodiments as discussed below may include optional steps, methods, andfeatures that one of ordinary skill should recognize as not being arequisite to fall within the scope of the present invention.

Referencing FIGS. 1-3, an image guided surgical system 100 in accordancewith the instant disclosure for use by a surgeon 101 or other personnelmay comprise a workstation 102 that includes a computer/controller andassociated software 104 communicatively coupled to one or more visualdisplays 106 and input devices 109 (e.g., keyboard, mouse, etc.) andsurgical instruments 170, 190 to facilitate surgical navigation relatedto an orthopedic replacement or revision surgery. In exemplary form, theinstant surgery will involve a total knee arthroplasty replacement orrevision procedure. Nevertheless, those skilled in the art willunderstand that the exemplary techniques, systems, software, andcomponents may be used as part of any orthopedic replacement or revisionsurgical procedure and by no means are limited to the knee.

In this exemplary embodiment, the associated software 104 includessurgical navigation software making use of tissue models (that mayinclude bone and soft tissue models) 114 that may be specific to thepatient 110. By way of example, imaging of the patient 110 may beundertaken during or in advance of surgery using any of the knownimaging modalities 112 sufficient for producing one or morepatient-specific virtual tissue models 114 including, but not limitedto, X-ray, fluoroscopy, ultrasound, CT, MM. From the data output usingat least one of the imaging modalities 112, one or more patient-specificvirtual tissue models 114 may be created using any of various methodsknown to those skilled in the art of bone reconstruction. For example,for knee surgeries, exemplary patient-specific virtual tissue models mayinclude, but are not limited to, bones of femur, tibia, and patella,cartilage associated with one or more of these bones, and connectiveligament tissue. As part of the virtual tissue models 114, the software104 may be uploaded with data reflecting the relative positions of thebones with respect to one another so that static poses of the models areavailable over a range of motion and, in addition or in the alternative,dynamic images of the models are available to show virtual motion of themodels with respect to one another across a range of motion. Thesedynamic images may be extracted directly from certain modalities, suchas, without limitation, fluoroscopy, or may be extrapolated usingcomputer simulation software making use of a plethora of static posesacross a range of motion.

The exemplary software 104 may make use of the virtual tissue models 114to create or incorporate a pre-operative surgical plan to achieve theknee replacement or revision. As part of an exemplary surgical plan,virtual models 120 of one or more orthopedic implants may be loaded orcreated and then test fit onto the virtual tissue models 114 in order toidentify the sizing of the implant(s), the bone cuts (resection cuts)needing to be made, and the proper placement of the eventual orthopedicimplant(s). By way of example, the exemplary software 104 incorporates astatic planner 122 that allows fitting of a virtual model of anorthopedic implant 120 onto at least one of the patient's virtual bonemodels 114 in order to assess fit, sizing, identification of anatomicallandmarks, and bone cut positions for receiving the eventual implant. Aspart of this static planner 122, once a virtual implant is chosen andits position is finalized with respect to the virtual tissue models 114,the planner may calculate the position of the bone cuts (for the actualpatient bone) needed to effectuate implantation of the orthopedicimplant. This static planner 122 is contrasted with an available dynamicplanner 124 as part of the software 102, which allows concurrentrepositioning of the virtual tissue models 114 and the orthopedicimplant models 120 as a unified unit so that one may assess kinematicfactors for determining implant type, shape, size, and position on theresected patient bone. Those skilled in the art are familiar withkinematic considerations surgeons utilize to differentiate betweenorthopedic implants and the factors a surgeon uses to choose anorthopedic implant using kinematic data. As part of this dynamic planner124, once a virtual implant is chosen and its position is finalized withrespect to the virtual tissue models 114, the planner may calculate theposition of the bone cuts (for the actual patient bone) needed toeffectuate implantation of the orthopedic implant.

After the pre-operative surgical plan is created or uploaded, one mayuse the preoperative plan to create custom instrumentation for thefemur, tibia, and/or patella, that includes, without limitation, patientanatomical mappers (PAMs) 130 and cutting guides 190.

A PAM 130 comprises a patient-specific device that matches the patientanatomy in only a single known position and orientation and may bemounted to the patient using surgical pins 210. By way of example, thePAM 130 may have one surface with a negative geometry precisely matingwith the patient anatomy (in other words, the surface shape of the PAMprecisely follows the surface, including shape changes, of the patientanatomy, so that a patient trough would reflect a PAM crest, while apatient crest would reflect a PAM trough). By utilizing a PAM that fitsto the patient anatomy in only a single location and orientation,instrumentation or other parts having known geometries (size, width,length, height, etc.) may be attached to the PAM to facilitatelocalization of position and orientation of the instrumentation or otherparts within a frame of reference utilized by the surgical navigationsoftware. In other words, because one knows the exact position andorientation of the PAM with respect to a patient anatomy (e.g., a bone),any structure (having known dimensions) rigidly mounted to the PAM willalso have a known position and orientation with respect to the patientanatomy. And a PAM may be utilized in combination with a cutting guide190.

In accordance with the instant disclosure, exemplary cutting guides 190may be aligned and positioned with the aid of the PAM 130. By way ofintroduction, an exemplary cutting guide 190 may be repositionablymounted to the PAM 130 so that the PAM is used for its referenceposition to know the position and orientation of the cutting guide withrespect to a patient's bone. Conversely, or in addition, the cuttingguide 190 may be disengaged from the PAM 130. In such an instance, thePAM 130 may be coupled to a pinner having orifices configured to receivean alignment pin in only a single orientation. Using the pinner, oncecorrectly positioned, two or more pins are inserted into a patient'sbone so that the pins align with orifices of an exemplary cutting guide(disjoined from the PAM 130). In this manner, an exemplary cutting guidemay be aligned by sliding over the pins in order to align the cuttingguide to make one or more bone cuts.

The pre-operative surgical plan may also be used to create computerinstructions, referred to herein as a patient case file or surgicalplan, that may be loaded into an associated surgical navigation softwareapplication 104 to facilitate real-time guidance of the relevantsurgical instrumentation. In addition, the instrumentation andinstruments needed for surgery, which may be created or chosen using thestatic 122 and/or dynamic planner 124, may be manufactured, packaged,sterilized, and assembled into a kit 500 for delivery in a just-in-timemanner.

Referring to FIG. 3, a distal femur 160 of the patient 110 may include arigid reference 170 attached to a patient bone, either via an existingsurgical incision or percutaneously. In exemplary form, the rigidreference 170 comprises a component of the image guided surgical system100 and may include a housing 174 mounted to a pair of pins 176 fastenedto the femur 160. The rigid reference 170 facilitates tracking of apatient bone 160 by the housing 174 coupling with or including aninertial measurement unit device 172 or other tracking device thatcommunicates (whether wired or wirelessly) with the surgical navigationworkstation 102. In exemplary form, an inertial measurement unit (IMUs)device 172 may include an inertial measurement unit (IMU) 173, abattery, and a wireless transmitter contained within a single housing,where the device 172 may be operative to create and transmit data to thesurgical navigation software application 104. Each IMU 173, 183 mayconsist of at least one triaxial accelerometer, one triaxialmagnetometer, and one triaxial gyroscope. In this manner, the IMU 173,183 generates data indicative of acceleration in three orthogonal axes,magnetic data, and gyroscopic data, which the surgical navigationsoftware application 104 uses to determine changes in position andorientation of the IMU. Accordingly, by having the IMU 173 rigidlymounted to the bone (e.g., femur 160) using the rigid reference 170,changes in position and orientation of the IMU can be quickly andaccurately attributed to changes in position and orientation for thebone. Thus, by knowing how the IMU 173 is being repositioned as afunction of time, the surgical navigation software application 104 isalso able to determine changes in position and orientation of the boneover the same time period. As will be discussed hereafter, byinitializing the IMU device 172 of the rigid reference 170 with respectto a second IMU device 182 associated with a cutting guide 190, arelative position of the cutting guide with respect to the patient bonecan be determined by the surgical navigation software application 104.

Turning back to FIG. 3, an exemplary cutting guide 190 in accordancewith the instant disclosure is configured to be repositionably mountedto a PAM 130 in order to guide a surgeon in making one or more bonecuts. This exemplary cutting guide 190 may be used for each of thefemoral and tibial resections as part of a total knee arthroplasty.

In this exemplary embodiment, the cutting guide 190 includes a guidebody 192 having at least one cutting slot 200 for guiding a surgicalsagittal saw or similar tool 250 (see FIG. 25) along a planar path tomake one or more bone cuts. The guide body 192 may also, separate fromor in addition to the slot 200, delineate one or more though orifices202 sized to allow throughput of a surgical pin 210. By way of example,each surgical pin 210 may be mounted to the patient's bone and beutilized to guide and couple to a fixed position cutting block 300 (seeFIG. 30). In this exemplary embodiment, the guide body 192 includes aneck 206 terminating at a receiver 208 configured to have mountedthereto the second inertial measurement device 182.

By way of example, the second inertial measurement device 182 mayinclude an inertial measurement unit (IMU) 183, a battery, and awireless transmitter contained within a single housing, where the device182 may be operative to create and transmit data to the surgicalnavigation software application 104.

As disclosed herein, each IMU 173, 183 may comprise three gyroscopes,three accelerometers, and three Hall-effect magnetometers (set of three,tri-axial gyroscopes, accelerometers, magnetometers) that may beintegrated into a single circuit board or comprised of separate boardsof one or more sensors (e.g., gyroscope, accelerometer, magnetometer) inorder to output data concerning three directions perpendicular to oneanother (e.g., X, Y, Z directions). In this manner, each IMU 173, 183may be operative to generate 21 voltage or numerical outputs from thethree gyroscopes, three accelerometers, and three magnetometers. Inexemplary form, each IMU 173, 183 may include a sensor board and aprocessing board, with a sensor board including an integrated sensingmodule consisting of three accelerometers, three gyroscopic sensors andthree magnetometers (LSM9DS, ST-Microelectronics) and two integratedsensing modules consisting of three accelerometers, and threemagnetometers (LSM303, ST-Microelectronics). In particular, the IMU 173,183 may also include angular momentum sensors measuring rotationalchanges in space for at least three axes: pitch (up and down), yaw (leftand right) and roll (clockwise or counter-clockwise rotation). In thismanner, the IMUs 173, 183 generates data indicative of acceleration inthree orthogonal axes, magnetic data, and gyroscopic data, which thesurgical navigation software application 104 uses to determine changesin position and orientation of each IMU.

By having the IMU 183 rigidly mounted to the cutting guide 190, changesin position and orientation of each IMU 173, 183 can be quickly andaccurately attributed to changes in position and orientation of thecutting guide with respect to the patient bone. Thus, by knowing how theIMU 183 is being repositioned as a function of time, the surgicalnavigation software application 104 is also able to determine changes inposition and orientation of the cutting guide 190 over the same timeperiod. As will be discussed hereafter, by initializing the IMU 173 ofthe rigid reference 170 with respect to the second IMU 183 associatedwith the cutting guide 190, a relative position of the cutting guidewith respect to the patient bone can be determined by the surgicalnavigation software application 104.

By way of example, the cutting guide 190 may have any number of knownpositions, such that when the cutting slot 200 is placed into one ofthese known positions, the position of the cutting slot 200 is knownrelative to the PAM 130. In order to repositionably mount the cuttingguide 190 to the PAM 130, a mechanical connection 220 existstherebetween that may include one or more joints. In exemplary form, themechanical connection 220 includes a lower joint 222, an adjuster 224,and an upper joint 226.

By way of example, the lower joint 222 may be at or near the connectionof the PAM 130 to the cutting slot 200. The lower joint 222 may comprisea revolute joint including a bolt or screw 230 (optionally springloaded) that may be tightened to selectively inhibit rotation of theadjuster 224 with respect to the PAM 130 and, accordingly, in a coarsesense adjust the position of the cutting slot 200. Alternatively, thelower joint 222 may be any joint or motion activated device (motordriven) that allows selective repositioning of the adjuster 224 withrespect to the PAM 130 so that, when desired, repositioning of theadjuster with respect to the PAM is substantially inhibited.

By way of example, the adjuster 224 may comprise an oblong or extendedring at least a portion of the lower joint 222 engages to fix andrelease the position of the adjuster with respect to the lower joint.Similarly, the adjuster 224 is also mounted to the upper joint 226which, in exemplary form, may comprise a revolute joint 234.

In exemplary form, the revolute joint 234 may include a bolt or screw240 (optionally spring loaded) that may be tightened to selectivelyinhibit rotation of the adjuster 224 with respect to the cutting guide190. Alternatively, the upper joint 226 may be any joint or motionactivated device (motor driven) that allows selective repositioning ofthe adjuster 224 with respect to the cutting guide 190 so that, whendesired, repositioning of the adjuster with respect to the cutting guideis substantially inhibited. In addition to the revolute joint 234, theupper joint 226 may also include a spherical joint 236. In this fashion,when the spherical joint is not locked, the cutting guide 190 may beangularly repositioned with respect to the adjuster 224 (and PAM 130) upto 45 degrees with respect to an axis extending parallel to therotational axis of the revolute joint 234. As will be discussed in moredetail hereafter, the adjustability of the spherical joint 236 may beutilized to adjust the varus or valgus nature of a distal femoral bonecut.

Turning to FIG. 4, an alternate exemplary rigid reference 270, that maybe used in lieu of or in addition to the rigid reference 170 of FIG. 3,comprises a reference housing 272, that includes an inertial measurementunit, mounted to a pair of pins 276 fastened to the femur 160. Thisalternate exemplary rigid reference 270 facilitates tracking of apatient bone 160 by communicatively coupling (whether wired 273 orwirelessly) the reference housing 272 (with the IMU 274) with areference transmitter located within a housing 278 that also houses apower supply (e.g., battery). In exemplary form, the relatively smallsize of the reference housing 272 allows it to be mounted to the patientbone 160 without requiring an additional incision or larger incision toaccess the surgical site of the joint replacement or revision. In otherwords, this alternate exemplary rigid reference 270 provides a sizeadvantage (smaller) over the other rigid reference 170 by not requiringthe transmitter and power supply be rigidly mounted to the patient bone.For example, the IMU is operative to create and convey data to thetransmitter, which passes the data onto the surgical navigation softwareapplication 104. The IMU 274 may consist of at least one triaxialaccelerometer, one triaxial magnetometer, and one triaxial gyroscope. Inthis manner, the IMU 274 generates data indicative of acceleration inthree orthogonal axes, magnetic data, and gyroscopic data, which thesurgical navigation software application 104 uses to determine changesin position and orientation of the IMU. Accordingly, by having the IMU274 rigidly mounted to the bone (e.g., femur 160) using the rigidreference 270, changes in position and orientation of the IMU can bequickly and accurately attributed to changes in position and orientationfor the bone. Thus, by knowing how the IMU 274 is being repositioned asa function of time, the surgical navigation software application 104 isalso able to determine changes in position and orientation of the boneover the same time period. As will be discussed hereafter, byinitializing the IMU device 274 of the rigid reference 270 with respectto the second IMU device 182 associated with the cutting guide 190, arelative position of the cutting guide with respect to the patient bonecan be determined by the surgical navigation software application 104.

Referencing FIG. 1 again, the workstation 102 running the surgicalnavigation software 104 is operative to process sensor data from theIMUs 173/274, 183 and convert this sensor data to information relatingto a resection plane location relative to the patient anatomy. Inaddition, the surgical navigation software 104 is operative to providevisualization to a surgeon via the one or more visual displays 106. Inexemplary form, visualization may include 3D virtual tissue models 114,3D virtual models of the cutting guide 190 or cutting slot 200,projections, text, or any other forms of communicating the orientationand position of the cutting slot relative to the patient anatomy. Theinformation communicated as part of the visualization may be updated ata minimum of ten frames per second so that the information beingdisplayed may be considered near real-time or real-time.

Any or all of the components of the cutting guide 190 may be disposablefor single-use. Alternatively, any or all of the components of thecutting guide 190 may be reusable and amenable to resterilization. Inany event, any or all of the components of the cutting guide 190, PAM130, and rigid references 170, 270 may be fabricated from numerousmaterials such as, without limitation, polymers, metals, and composites,and may be fabricated using techniques including, but not limited to,additive manufacturing, injection molding, machine milling, and casting.Assembly and connection of individual components of cutting guide 190,PAM 130, and rigid references 170, 270 may be performed by any meansavailable, such as appropriate press fitting, locking, utilization ofexternal fixation devices such as set screws, adhesives, welding, orother methods known to those skilled in mechanical assemblies to securecomponents to one another. While various components of the cutting guide190, PAM 130, and rigid references 170, 270 may have been discussedseparately herein, it is understood that any or all the components maybe integrated or separable.

Referring to FIG. 5, to provide real-time feedback as to the positionand orientation of the cutting slot 200, IMUs 173/274, 183 are operativeto generate data indicative of orientation and position, which iscommunicated to the surgical navigation software 104 running on theworkstation 102. The following is a discussion of how orientation andposition of the cutting slot 200 are determined by the surgicalnavigation software 104 when teamed with known dimensions for thesurgical equipment (e.g., cutting guide 190, PAM 130) in an exemplaryprocedure for a total knee arthroplasty (TKA).

IMUs 173/274, 183 in accordance with the instant disclosure may measureorientation about an x-axis, y-axis, and z-axis, but may not directlymeasure translation. In order to determine translation of the IMUs, onemay use external sensors or have the IMUs initialized using a startingposition and orientation that is known with respect to a real-worldobject (e.g., a bone). For example, the external sensors may compriselinear positioning sensors (e.g. linear variable displacementtransformer, linear motion encoder, ultrasonic ranging, or opticalranging) to provide translation information.

In exemplary form, as discussed hereafter, the instant disclosure maymake use of an initialization position where the IMUs 173/274, 183 arerigidly mounted to the cutting guide 190 and PAM 130, respectively, sothat the relative position and orientation of the cutting guide withrespect to the PAM is known (and the relative position and orientationof the IMUs 173/274, 183 is also known). By way of further example, thisinitialization position may have cutting slot 200 aligned along the sameplane as the PAM. After establishing this initialization position, thecutting guide 190 may be repositioned with respect to the PAM 130 tocarry out the femoral bone cuts established via the pre-operativesurgical plan.

In the context of the instant disclosure, pre-operative surgicalplanning will establish the depth (e.g., location) of the distal bonecut for a TKA, as well as the placement of the PAM 130 on the patientbone 160. As depicted in FIG. 5, with the depth of the distal bone cutknown, identified as “x”, and the starting position B known from theplacement of the PAM 130 with respect to the bone 160, two pieces ofinformation are required in order to position the cutting guide 190correctly to effectuate the distal cut: (1) the angle α; and (2) thedistance AB. The distance AB is a function of known instrumentdimensions (this is the linear distance from the center of the PAM tothe center of the cutting slot 200), where the distance AB is constantin accordance with the instant disclosure and does not change as thecutting guide 190 is rotated about the PAM 130 via the lower joint 222.As a result, using trigonometry, one can calculate the angle α from theequation of FIG. 5. And knowing this angle α, the surgical navigationsoftware 104 tracks the angular change of the cutting slot 200, via theIMU 173, 274, relative to the patient bone using the IMU 183 of the PAM130, so that when cutting slot is positioned at angle α, the surgicalnavigation software informs the surgeon the cutting slot is positionedin accordance with the pre-operative surgical plan, so that the surgeonmay carry out the distal femoral bone cut. In case the cutting slot 200is not aligned with angle α, the surgical navigation software providesfeedback to the surgeon indicating how the cutting slot should berepositioned to achieve angle α. As will be discussed hereafter, thejoints 226, 236 associated with the cutting guide 190 may berepositioned to adjust for varus/valgus, flexion/extension, and otherknown degrees of freedom.

In accordance with the instant disclosure, knowing the instrument (PAM130, cutting guide 190) dimensions is important for calculating therelative position and orientation of the instruments dynamically duringa surgical procedure, such as TKA. For example, each of the PAM 130,cutting guide 190, and cutting slot 200 may be appropriately sized tofacilitate performing the desired surgery, preferably with minimalmodification to the standard incision or minimally invasive incision.Appropriate dimensions for each component (e.g., the PAM 130, cuttingguide 190, and cutting slot 200) may be selected prior to surgery inmany ways. For example, each component may be made in a patient-specificmanner, where all dimensions are selected to best match the patient andthe surgical plan. Because patient-specific manufacturing may not becost effective, another option is to choose dimensions based onpopulation analysis. Those skilled in the art of orthopedicinstrumentation will be familiar with sizing based on populationanalysis.

In general, a dimension of the anatomy is measured across severalsamples—a population—so that the range and variation of measurement isknown across the samples. If desired, the population may be subdividedso that the range and variation of the measurement within eachpopulation subdivision is known. Methods of performing this subdivisioninclude, but are not necessarily limited to, building regression models,unsupervised or supervised clustering, mixture modeling, partitioning,or any other methodology. In such a way, the best set of dimensions, orsizes, may be chosen for each component. This process may be performedin an automatic or semi-automatic way using statistical geometricalmodels or machine learning methods.

Using the known dimensions of component parts of each instrument,including post assembly, one can determine the allowable working volumeof the surgical instrument—specifically the reachable cut orientationand positions—using methods familiar to those skilled in the art ofrobotic manipulators and forward kinematics. For example, theDenavit-Hartenberg (DH) parameters of each joint are known given thetype of joint—revolute, spherical, or any other—and the known dimensionsof each linkage of the mechanical connection 220 as outlined above. Fromthis information the DH convention may be used to establish theappropriate series of transformations between the first revolute joint222 and the cutting slot 200. By calculating the end position andorientation at all or most of the allowable range of the variables foreach joint, the working volume of the cutting slot 200 can be calculatedfor each of the steps in the surgical procedure. This convention may beused to verify that the chosen component dimensions are sufficient toachieve the desired surgical plan. FIGS. 6-15 show some possiblecritical dimensions of component parts of the system 100 as well asexamples of population variations, which serve as inputs to dimensionalchoice.

Referencing FIG. 6, the PAM 130 may include critical dimensions, inaddition to the patient specific features, comprising the (mediolateral)ML width and (anteroposterior) AP height. In this exemplary disclosure,the PAM 130 sets the center of rotation for the cutting guide 190, wherethe location of the PAM 130 can be selected to optimize the accuracy andperformance of the system 100. The AP and ML dimensions should becarefully chosen so that the mechanical connection 220 coupling the PAM130 to the cutting guide 190 clears both the intended incision and themedial aspect of the femora without causing impingement of the cuttingguide with the bone or soft tissue once assembled. Similarly, the lengthof the cutting guide 190, as well as the location of the lockingpositions via the mechanical connection 220, should be selected tofacilitate each of the procedural steps—allowing the cutting slot 200 tobe properly positioned and manipulated without impingement.

Referencing FIG. 7, an exemplary method for establishing and optimizingthe mating site of the PAM 130 on the patient bone 160 includesutilization of a trained human expert as part of the pre-operative planor, in addition to or in lieu of, using artificial intelligence (AI). AIlearns the design constraints with regard to accuracy and the populationmorphology using measurements or surface geometry extracted frompopulation statistics (i.e. statistical atlas), and outputs a locationof the PAM 130 optimized for accuracy to achieve the desired plan.

Turning to FIGS. 8 and 9, an exemplary cutting guide 190 in accordancewith the instant disclosure may include a cutting slot 200 havingdimensions that may be, configured in part, based upon the intended sawblade a surgeon anticipates using during the TKA, in order toappropriately capture the saw blade. In many TKA procedures, surgeonswill utilize an oscillating tip saw to remove bone from the distal femurto prepare the femur to accept an orthopedic implant. Exemplary sawblades for an oscillating tip saw may have a thickness of approximately1.19 millimeters, though other thickness may be used from time-to-time.In this manner, the width of the cutting slot 200 (in the AP direction)may be slightly greater than the thickness of the intended saw blade.The more precise the tolerance between the cutting slot 200 width andthe saw blade results in greater precision that the bone cut of theblade is coplanar with the slot. In addition to establishing the APwidth of the cutting slot 200, the ML length of the cutting slot shouldbe chosen to allow resection of the entire distal, posterior andanterior surfaces as dictated by the pre-operative surgical plan.

Referring to FIG. 10, an alternate exemplary cutting guide 290 includesa guide body 292 that replaces the cutting slot 200 with at least twoguide pin holes 294. In this alternate exemplary cutting guide 290, theguide pin holes 294 match corresponding holes of a separate cuttingblock 300 (see FIG. 30) so that the guide 290 can be utilized toposition two or more surgical pins 210 that are then utilized to alignthe cutting block. In other words, the cutting guide 290 is utilized bythe surgeon to know where the drill holes and correspondingly fastensurgical pins 210 to the patient's bone. By way of further example, thepin holes drilled (or the position of the surgical pins themselves) intothe patient's bone may be of the same distance from one another as thepin holes on a conventional distal cutting block 300. Post drilling ofthe pin holes, the guide 290 may be replaced with a separate cuttingblock, which is aligned to the patient's bone using the surgical pins.By way of example, exemplary conventional cutting blocks are availablefrom Smith & Nephew, Zimmer, DePuy, and Stryker.

Looking at FIG. 11, the exemplary cutting guide 190 may include a bladesupport attachment 195 selectively coupled to the guide body 192 inorder to provide stability to the surgical blade extending through thecutting slot 200.

FIGS. 12-16 reflect an exemplary process for automatic landmarking ofthe patient bone model 114, this this case the femur, using thepre-operative surgical planning software 104. As depicted in FIG. 12,the software 104 is operative to use statistical atlas automaticlandmarking to compute the location of the mechanical axis, the distalresection point, which are both used to compute the suggested, preferredfemoral distal resection plane 156. FIG. 13 depicts extraction andmeasurement of the medio-lateral width of the resection across a givenpopulation of the statistical atlas. The extracted and measuredmedio-lateral widths are used to create the design envelope for thedistal cutting slot 200 dimensions (representatives from the statisticalatlas population are depicted, with blue reflecting the largest size,green depicting a medium size, and red reflecting the smallest size).FIG. 14 shows the distal femoral resection cuts made to representativesof the statistical atlas. FIG. 15 reflects the relationship betweenresected medio-lateral dimensions and changes in distal resection plane156 depth. For instance, the yellow color reflects positioning theresection plane 156 4 millimeters more distal than the planned orsuggested resection plane location, whereas red reflects positioning theresection plane at the planned or suggested location and, finally, lightblue reflects positioning the resection plane 4 millimeters moreproximal than the planned or suggested resection plane location.Finally, FIG. 16 depicts medio-lateral widths across the statisticalatlas population to establish cutting slot 200 dimensions that capturemost or all of a given population.

Turning to FIGS. 17-20, as an early step in surgical navigation,registration is undertaken to align the image guided surgical system 100to the patient bone 160. As part of establishing registration, the PAM130 may be aligned to the patient bone 160 so that the patient specificsurface(s) of the PAM match and precisely contact the patient anatomy inonly a single orientation and position. Upon positioning the PAM 130 onthe patient bone 160 so the PAM occupies the single orientation andposition matching precisely the topography of the tissue (e.g., bone),the PAM may be mounted to the patient tissue (e.g., bone) using one ormore surgical pins 210 or screws that are received within holes that maybe drilled in to the patient tissue. In this fashion, the PAM 130 isrigidly affixed to the patient tissue so that as the tissue isrepositioned, so too is the PAM. In addition to mounting the PAM 130 topatient tissue, the rigid reference 170 is also mounted to patienttissue. As discussed herein, the cutting guide 190 is repositionablymounted to the PAM 130 via the mechanical connection.

As depicted in FIGS. 17 and 18, in exemplary form, the cutting guide 190is mounted to the PAM 130 in a known registration position andorientation using the mechanical connection 220, which is in turn aknown position and orientation relative to the patient bone 160 (e.g.,the femur) by way of the PAM. More specifically, as depicted in FIG. 17,the lower joint 222 couples the PAM 130 to the adjuster 224, and theupper joint 226 couples the cutting guide 190 to the adjuster. Inparticular, the cutting guide 190 is oriented so that a dominantlongitudinal axis of the cutting slot 200 is parallel to a dominantlongitudinal axis of the cutting guide so the axes are co-planar. Inaddition, a spacing is set between the cutting guide 190 and the PAM130, along the adjuster 224 using the joints 222, 226, that correspondsto a predetermined spacing that is known. In this manner, the positionof the cutting guide 190 in solid lines is the predetermined positionwith respect to the PAM 130. It should be noted that by adjusting therevolute lower joint 222, the cutting guide 190 may be rotated about thePAM 130 as depicted in phantom lines. When the cutting guide 190 ismounted to the PAM 130, via the mechanical connection 220, and assumesthe known registration position (and when the rigid reference 170 ismounted to the patient tissue), data from the IMUs 173, 183 is recordedby the image guided surgical system 100 to establish a point ofreference. More specifically, data from the IMUs 173, 183 is processedto determine changes in position and orientation of the cutting guide190 with respect to the patient bone 160. In this fashion, futuremotions of the patient bone 160 are tracked independently using the IMU173 of the rigid reference 170, while motions of the cutting guide 190are tracked separately using the tracking IMU 183. As a result, asdepicted in FIG. 18, the image guided surgical system 100 displays avirtual bone model 114 of the patient's bone 160 along with a phantomline 185 denoting the position and orientation of the cutting slot 200(that may be color highlighted (e.g., green)) to differentiate between aposition of the cutting slot that is or is not consistent with apre-operative surgical plan establishing the position and orientation ofa bone cutting plane.

Turning to FIGS. 19 and 20, establishing registration of the cuttingguide 190 with respect to the patient bone may also includerepositioning of the cutting guide with respect to the mechanicalconnection 220 using the upper spherical joint 236. In exemplary form,the upper spherical joint 236 allows the guide body 192 to selectivelyallow the guide body (and cutting slot 200) to be angularly repositionedwith respect to the adjuster 224 (and PAM 130) up to 45 degrees withrespect to an axis extending parallel to the rotational axis of therevolute joint 234. In this manner, the spherical joint 236 allows forvarus or valgus adjustment of the cutting slot 200. By way of example,the solid line position of the cutting guide 190 body 192 isrepresentative of the registration position, whereas the phantom linesare representative of possible changes in angular orientation that theguide body 192 may occupy with respect to the rotational axis of therevolute joint 234. Because the IMU 183 is rigidly mounted to the guidebody 192, changes in the position and orientation of the cutting slot200 are correspondingly reflected in changes in position and orientationof the IMU 183, which sends its data to the image guided surgical system100. The image guided surgical system uses the data from the IMU 183,along with knowing the dimensions of the guide body 192 and the positionof the spherical joint 236 with respect thereto, to calculate theposition and orientation of the cutting slot 200. As a result, asdepicted in FIG. 20, the image guided surgical system 100 displays avirtual bone model 114 of the patient's bone 160 along with a pair ofphantom lines 187, 189 denoting the position and orientation of thecutting slot 200 (that may be color highlighted (e.g., white 189)) withrespect to the position and orientation of the intended cutting slot(that may be color highlighted (e.g., green 187)) to differentiatebetween a position and/or orientation of the cutting slot that is or isnot consistent with a pre-operative surgical plan establishing theposition and orientation of a bone cutting plane. Post registration, theimage guided surgical system 100 may be utilized to facilitate one ormore bone cuts at a distal end of the femur as part of a TKA.

Referring to FIG. 22, a TKA surgery may include a distal femoralresection. After registration of the image guided surgical system 100 aspreviously described, the cutting guide 190 may be repositioned withrespect to the PAM using one or both of the joints 222, 226. By way ofexample, the lower revolute joint 222 may be manipulated so as to allowthe cutting guide 190 to rotation around the PAM 130 via a rotationalaxis extending through the bolt/screw 230 in preparation for the distalfemoral resection. In exemplary form, the image guided surgical system100 may be operative to process data from the IMUs 173, 183 and displayvirtual bone model 114 of the patient's bone 160 and the relativeupdated position and orientation of the cutting slot 200 fromcalculating the relative position and orientation of the cutting guide190 with respect to the patient's bone. In the context of the lowerjoint 222, because only a single revolute joint is used, the one or morevisual displays 106 may show a “reachable” region, or the allowablerange of bone that may be cut by manipulating the upper spherical joint.In particular, using trigonometry, the image guided surgical system 100calculates the distal-to-proximal distance “depth₁” by taking the knowdistance “l_(RI_1)” between the first and second joints 222, 226 andmultiplying by the sine θ, where angle θ is the angle between theregistration position of the cutting guide 190 and the current positionof the cutting guide. Using data from the IMUs 173, 183, the imageguided surgical system 100 is operative to calculate the position of thecutting guide and, correspondingly, calculate angle θ. Using thecalculated angle θ, the image guided surgical system 100 then calculates“depth₁” and depicts the virtual bone model 114 of the patient's bone160 and the relative updated position and orientation of the cuttingslot 200. In this fashion, the surgeon is able to determine whether thecutting guide 190 should be further rotated with respect to the PAM 130in accordance with the pre-operative surgical plan to make the correctdistal femoral bone cut. Presuming the “depth₁” of the femoral bone cutis reached, the surgeon may lock the lower joint 222 in position andfocus on repositioning the upper joint 226.

Turning to FIG. 23, the upper joint 226 may include a revolute joint 234and a spherical joint 236. Each may be repositioned to adjust theposition of the cutting guide 190 with respect to the PAM 130. Inexemplary form, the cutting guide 190 may be allowed to rotate around arotational axis extending through the bolt/screw 240. Rotation about thebolt/screw 240 may be used to correct for (or make adjustments to) theflexion and extension angle for resection. In particular, usingtrigonometry, the image guided surgical system 100 calculates thedistal-to-proximal distance “depth₂” by taking the know distance“l_(RI_2)”, between the second joint 226 and the center of the cuttingguide body 192, and multiplying by the sine σ, where angle σ is theangle between the registration position of the cutting guide 190 and thecurrent position of the cutting guide with respect to upper joint 226.Using data from the IMUs 173, 183, the image guided surgical system 100is operative to calculate the position of the cutting guide 190 and,correspondingly, calculate angle σ. Using the calculated angle σ, theimage guided surgical system 100 then calculates “depth₂” and depictsthe virtual bone model 114 of the patient's bone 160 and the relativeupdated position and orientation of the cutting slot 200. In thisfashion, the surgeon is able to determine whether the cutting guide 190should be further rotated with respect to the second joint 226 inaccordance with the pre-operative surgical plan to make the correctdistal femoral bone cut. Presuming the “depth₂” of the femoral bone cutis reached, the surgeon may lock the upper revolute joint 234 inposition and focus on repositioning the spherical joint 236.

As depicted in FIG. 24, adjustment of the spherical joint 236 allows forrotation of the cutting slot 200 to accommodate for varus and valgusangular adjustments. In other words, unlocking the spherical joint 236allows the cutting slot 200 to be manipulated so that the resectiondepth, varus orientation, and flexion orientation of the cut isacceptable relative to a pre-operative plan. In exemplary form, thecutting guide 190 may be allowed to rotate around a sphere of thespherical joint 236. In particular, using trigonometry, the image guidedsurgical system 100 calculates medial compartment offset and lateralcompartment offset using the following equations:

λ=proj(q _(current))

depth_(3M) =l _(RI_3M) *a sin(λ)

depth_(medial)=depth₁+depth₂+depth_(3M)

depth_(3L) =l _(RI_3L) *a sin(λ)

depth_(lateral)=depth₁+depth₂+depth_(3L)

where:

“l_(RI_3M)” is the length of the guide body 192 across the medialcompartment;

“l_(RI_3L)” is the length of the guide body 192 across the lateralcompartment;

angle “λ” is the angle between the registration position and the angularoffset.

Referring to FIGS. 22-26, presuming the “depth₂” of the femoral bone cutis reached, the surgeon may lock the upper revolute joint 234.Accordingly, to get the medial depth offset “depth_(3M)”, the knownlength of “l_(RI_3M)” is multiplied by sine λ. Likewise, to get thelateral depth offset “depth_(3L)”, the known length of “l_(RI_3L)” ismultiplied by sine λ. In order to calculate the actual resection depthin the medial compartment, “depth₁” and “depth₂” and “depth_(3M)” aresummed (see FIGS. 22-24). Similarly, to calculate the actual resectiondepth in the lateral compartment, “depth₁” and “depth₂” and “depth_(3L)”are summed (see FIGS. 22-24). Using data from the IMUs 173, 183, theimage guided surgical system 100 is operative to calculate theforegoing. In this fashion, the surgeon is able to determine whether thecutting guide 190 should be further rotated about the spherical joint236 in accordance with the pre-operative surgical plan to make thecorrect distal femoral bone cut. Once the position and orientation ofthe cutting guide 190 is acceptable, the joints 222, 226, 236 may belocked and the distal femoral resection cut may be undertaken, asdepicted in FIGS. 25 and 26, with a surgeon controlling a surgical saw250.

Referring to FIGS. 27-30, after the distal femoral resection cut iscompleted, the cutting guide 190 and PAM 130 may be used to facilitateplacement of fixation devices (e.g., surgical pins 210) that will guideand engage a fixed position cutting block 300. In femoral TKA surgicalprocedures, having five bone cuts, the remaining cuts (besides thedistal femoral resection) are the anterior, posterior, and two chamfercuts. To facilitate these four bone cuts, one may make use of aconventional instrument, referred to as the 4-in-1 cutting block 300.This cutting block 300, which is fixed to the distal end of a patient'sresected femur 160, includes two or more openings configured to receivetwo or more surgical pins 210 extending from the resected distalsurface. In this fashion, the surgical pins 210 are operative to alignthe cutting block 300 with respect to the distal femur and to guide thecutting block into position against the resected femur surface. Inaddition to the openings configured to receive the surgical pins 210,the cutting block 300 includes four or more cutting slots, each cuttingslot belonging to one of the four mentioned remaining bone cuts. Itshould be noted, however, that different knee implants may requiredifferent cutting positions and even different numbers of bone cuts.Nevertheless, the exemplary devices and methods disclosed herein may beapplied to any cutting guide (e.g., smart or dumb) whether placed byphysical alignment guides or via computer feedback or control.

As depicted in FIGS. 28 and 29, in order to prepare the resected femurfor using the 4-in-1 cutting block 300, the image guided surgical system100 provides instructions via the one or more visual displays 106 forrepositioning the cutting guide 190 so that the guide body 192 ispositioned against the exposed surface of the resected distal femur 107based upon data from the IMUs 173, 183. In particular, the guide body192 is positioned so that one or more though orifices 202 are alignedwith intended locations of the resected femur 107 so that a surgicaldrill may extend through the orifices and drill out holes within thefemur. The pin holes dictate the internal-external rotation andanterior-posterior positioning of the remaining bone cuts. Post holecreation, two or more surgical pins 210 are placed, one in each hole,optionally using the guide body orifices 202 to align the surgical pinsinto position so that the surgical pins extend into the resected femurand extend distally generally perpendicular to the resected, femoralplanar surface. After the surgical pins 210 are mounted to the resectedfemur, the cutting guide 190 and PAM 130 may be removed from thesurgical site.

Turning to FIGS. 30 and 31, with the surgical pins 210 in position onthe resected femur 107, a 4-in-1 cutting block 300 is aligned withrespect to the distal resected femur 107 so that two or more openings ofthe cutting block 300 are configured to receive the two or more surgicalpins 210 so that the cutting block may be repositioned against theexposed bone surface of the distal femoral resection cut. With thecutting block aligned using the surgical pins 210 and against theresected distal femur surface, the surgeon may lock the cutting block300 in position. Thereafter, the surgeon may reposition a surgical bladethrough the respective slots 302 of the block 300 to make the anterior,posterior, and two chamfer distal femur cuts. After completion of thebone cuts (see FIG. 31), the block 300 and surgical pins 210 may beremoved from the distal femur in anticipation of orthopedic trialfitting. While the foregoing exemplary surgical procedure makes use of a4-in-1 cutting block 300 to make the anterior, posterior, and twochamfer distal femur cuts, it is also within the scope of the disclosureto utilize the cutting guide 190, the PAM 130, and a guide foot 260.

Referencing FIGS. 32-37, after the distal femoral resection cut iscompleted, the cutting guide 190 and PAM 130 may be used to facilitateplacement of fixation devices (e.g., surgical pins 210) that will guideand engage the guide foot 260. As discussed herein, femoral TKA surgicalprocedures generally include five bone cuts, four of which remain afterthe distal femoral resection has been completed. To facilitate thesefour bone cuts, one may make use of the guide foot 260 that replaces thePAM 130 as the anchor to which the mechanical connection 220 and thecutting guide 190 are mounted.

As depicted in FIG. 32, after the PAM 130, mechanical connection 220,and cutting guide 190 have been utilized to position the surgical pins210, the foregoing components may be removed from the surgical site. Inexemplary form, the PAM 130 is replaced with a guide foot 260 thatconnects to the mechanical connection 220 just as the PAM did, so thatthe guide foot, mechanical connection, and cutting guide 190 are mountedto one another. In exemplary form, the guide foot 260 includes two ormore orifices configured to receive, respectively, the surgical pins 260extending from the resected portion of the femur 107. The orifices ofthe guide foot 260 are configured to receive the surgical pins 210 inonly a single orientation so that, when the guide foot receives thesurgical pins and is repositioned against the resected femur 107 andaffixed in position, the image guided surgical system 100 knowsprecisely the position and orientation of the guide foot with respect tothe femur.

In this exemplary embodiment, the image guided surgical system 100 isprogrammed with the precise dimensions of the guide foot 260 so thatwhen the guide foot is in a registration position, the position of thecutting guide 190 with respect to the femur is known. In other words,the cutting guide 190 is mounted to the guide foot 260 in a knownregistration position and orientation using the mechanical connection220, which is in turn a known position and orientation relative to thepatient bone 160 (e.g., the femur) by way of the guide foot.

As discussed herein, the lower joint 222 couples the guide foot 260 tothe adjuster 224, and the upper joint 226 couples the cutting guide 190to the adjuster. In particular, the cutting guide 190 is oriented sothat a dominant longitudinal axis of the cutting slot 200 is parallel toa dominant longitudinal axis of the cutting guide so the axes areco-planar. In addition, a spacing is set between the cutting guide 190and the guide foot 260, along the adjuster 224 using the joints 222,226, that corresponds to a predetermined spacing that is known. In thismanner, the position of the cutting guide 190 is known with respect tothe guide foot 260. When the cutting guide 190 is mounted to the guidefoot 260, via the mechanical connection 220, and assumes the knownregistration position (and when the rigid reference 170 is mounted tothe patient tissue), data from the IMUs 173, 183 is recorded by theimage guided surgical system 100 to establish a point of reference forthe cutting guide 190 having a known position and orientation withrespect to the resected femur. And, as discussed hereafter, this pointof reference is utilized by the image guided surgical system 100 totrack and inform a user (e.g., a surgeon) concerning the position andorientation of the cutting guide to facilitate utilizing the cuttingguide to perform the anterior, posterior, and two chamfer distal femurcuts.

Referring to FIGS. 34 and 35, data from the IMUs 173, 183 is processedby the image guided surgical system 100 to determine changes in positionand orientation of the cutting guide 190 with respect to the patientbone 160. In this fashion, motions of the patient bone 160 are trackedindependently using the IMU 173 of the rigid reference 170, whilemotions of the cutting guide 190 are tracked separately using thetracking IMU 183. As a result, the image guided surgical system 100displays a virtual bone model 114 of the patient's bone 160 along with aphantom line 310 color coded (e.g., green) to confirm that the intendedcut line is in accordance with a pre-operative surgical plan. In thisexemplary sequence, the surgeon may reposition the cutting guide 190 byloosening and tightening the revolute joints 222, 234 and the sphericaljoint 236 in order to position and orient the cutting slot 200 to makethe requisite cuts in accordance with the pre-operative surgical plan,namely the anterior cut as depicted in FIG. 34. The one or more visualdisplays 106 are updated in real-time or near real-time to depict thebone model 114 consistent with the position and orientation thepatient's actual bone with respect to the projected cutting line, whichpasses through the cutting slot 200. Consequently, when the cuttingguide 190 is positioned and oriented consistent with the pre-operativesurgical plan, the surgeon may visually confirm the position using theone or more visual displays 106 and carry out the bone cut by using asurgical saw 250 having a blade received within the cutting slot 200.This process is repeated by repositioning the cutting guide 190 vialoosening and tightening the revolute joints 222, 234 and the sphericaljoint 236 in order to reposition and reorient the cutting slot 200 toalso make the posterior cut (see FIG. 36), the anterior chamfer cut (seeFIG. 37), and the posterior chamfer cut (see FIG. 38). After making thelast four (or so) bone cuts using the cutting guide 190, the cuttingguide, mechanical connection 220, and the guide foot 260 may be removedfrom the surgical pins 210 and away from the surgical site. Likewise,the surgical pins 210 may be removed from the distal resected femur toaccommodate orthopedic trial test fitting. But the instant embodimentscan also be used with bone cuts beyond the distal femoral cuts.

Referencing FIGS. 39 and 40, it is also in accordance with the instantdisclosure that the image guided surgical system 100 be utilized toguide bone cuts beyond those of the distal femur. By way of example, theimage guided surgical system 100 may be utilized to carry out the tibiaresection as part of a TKA procedure (revision or replacement). Forexample, the image guided surgical system 100 may make use of the sameworkstation 102, software 104, visual displays 106, mechanicalconnections 220, and surgical instruments 170, 190. But what differs arethe patient-specific virtual tissue models 114 (which comprise aproximal tibia, rather than a distal femur discussed above) and the PAM130 (PAM for femur is not the same as the PAM for the tibia).

In this exemplary discussion, the PAM 130 is configured to have at leastone surface with a geometry matching the negative of the patient'sproximal tibia (in other words, the surface shape of the PAM preciselyfollows the surface, including shape changes, of the patient's proximaltibia). By utilizing a PAM 130 that fits to the patient's tibia in onlya single location and orientation, instrumentation or other parts havingknown geometries (size, width, length, height, etc.) may be attached tothe PAM to facilitate localization of position and orientation of theinstrumentation or other parts within a frame of reference utilized bythe surgical navigation software 104. In other words, because one knowsthe exact position and orientation of the PAM 130 with respect to apatient's tibia, any structure (having known dimensions) rigidly mountedto the PAM will also have a known position and orientation with respectto the patient's tibia. In this fashion, the PAM 130 operates tocorrelate the virtual frame of reference with the real-world frame ofreference.

In the context of the instant disclosure, virtual pre-operative surgicalplanning may establish the position and orientation of the proximaltibia resection bone cut for a TKA, as well as the placement of the PAM130 on the patient's tibia 162. As part of this pre-operative surgicalplanning, the image guided surgical system 100 makes use of aregistration to align the image guided surgical system to the patient110. As part of establishing registration, the PAM 130 is aligned to thepatient so that the patient specific surface(s) of the PAM match andprecisely contact the patient's tibia in only a single orientation andposition. Upon positioning the PAM 130 on the patient's tibia 162 so thePAM occupies the single orientation and position matching precisely thetopography of the tibia, the PAM may be mounted to the tibia using oneor more surgical pins 132 or screws that are received within holes thatmay be drilled into the tibia. In this fashion, the PAM 130 is rigidlyaffixed to the tibia so that as the tibia is repositioned, so too is thePAM. In addition to mounting the PAM 130 to patient tissue, a rigidreference (not shown) is also mounted to the tibia. Similarly, asdiscussed before, the cutting guide 190 is repositionably mounted to thePAM 130 via the mechanical connection 220.

In exemplary form, the cutting guide 190 is mounted to the PAM 130 in aknown registration position and orientation using the mechanicalconnection 220, which is in turn a known position and orientationrelative to the patient bone (e.g., the tibia 162) by way of the PAM.Consistent with the prior discussion, the lower joint 222 couples thePAM 130 to the adjuster 224, and the upper joint 226 couples the cuttingguide 190 to the adjuster. In particular, the cutting guide 190 may beoriented so that a dominant longitudinal axis of the cutting slot 200 isparallel to a dominant longitudinal axis of the cutting guide so theaxes are co-planar. In addition, a spacing is set between the cuttingguide 190 and the PAM 130, along the adjuster 224 using the joints 222,226, that corresponds to a predetermined spacing that is known. Itshould be noted that by adjusting the revolute lower joint 222, thecutting guide 190 may be rotated about the PAM 130. When the cuttingguide 190 is mounted to the PAM 130, via the mechanical connection 220,and assumes the known registration position (and when the rigidreference 170 is mounted to the patient tissue), data from the IMUs 173,183 is recorded by the image guided surgical system 100 to establish apoint of reference. More specifically, data from the IMUs 173, 183 isprocessed to determine changes in position and orientation of thecutting guide 190 with respect to the patient bone 162. In this fashion,future motions of the tibia 162 are tracked independently using the IMU173 of the rigid reference 170, while motions of the cutting guide 190are tracked separately using the tracking IMU 183. As a result, theimage guided surgical system 100 displays a virtual bone model 114 ofthe tibia along with a visual reference denoting the position andorientation of the cutting slot 200 (that may be color highlighted(e.g., green)) to differentiate between a position of the cutting slotthat is or is not consistent with a pre-operative surgical planestablishing the position and orientation of a bone cutting plane.

Because the IMU 183 is rigidly mounted to the guide body 192, changes inthe position and orientation of the cutting slot 200 are correspondinglyreflected in changes in position and orientation of the IMU 183, whichsends its data to the image guided surgical system 100. The image guidedsurgical system uses the data from the IMU 183, along with knowing thedimensions of the guide body 192 to calculate the position andorientation of the cutting slot 200. As a result, the image guidedsurgical system 100 may display a virtual bone model 114 of thepatient's tibia 162 along with a pair of phantom lines denoting theposition and orientation of the cutting slot 200 (that may be colorhighlighted (e.g., white)) with respect to the position and orientationof the intended cutting slot (that may be color highlighted (e.g.,green)) to differentiate between a position and/or orientation of thecutting slot that is or is not consistent with a pre-operative surgicalplan establishing the position and orientation of the tibia resectioncut. Post registration, the image guided surgical system 100 may beutilized to facilitate the tibia resection cut.

Referring again to FIGS. 39 and 40, the cutting guide 190 may berepositioned with respect to the PAM 130 using one or both of the joints222, 226. By way of example, the lower revolute joint 222 may bemanipulated so as to allow the cutting guide 190 to rotation around thePAM 130 via a rotational axis extending through the bolt/screw 230 inpreparation for the distal femoral resection. In exemplary form, theimage guided surgical system 100 may be operative to process data fromthe IMUs 173, 183 and display virtual bone model 114 of the patient'stibia 162 and the relative updated position and orientation of thecutting slot 200 from calculating the relative position and orientationof the cutting guide 190 with respect to the patient's tibia. In thecontext of the lower joint 222, because only a single revolute joint isused, the one or more visual displays 106 may show a “reachable” region,or the allowable range of proximal tibia that may be cut by manipulatingthe upper spherical joint. In particular, as discussed herein, usingtrigonometry, the image guided surgical system 100 the position of thecutting slot 200 using data from the IMUs 173, 183. Upon reaching theappropriate position, as confirmed by the visual displays 106, thesurgeon may utilize a surgical saw blade (not shown) extending into thecutting slot 200 in order to remove the proximal section of the tibia.After making the tibia resection cut, the rigid reference 170, PAM 130,mechanical connections 220, and cutting guide 190 may be removed fromthe surgical site. In the alternative, the rigid reference 170 may bemaintained as part of positioning an orthopedic trial or permanentimplant.

Turning to FIG. 41, it is also within the scope of the disclosure toremove the second inertial measurement device 182 from the cutting guide190 and mount the inertial measurement device to a placement device 400.In such a circumstance, the second inertial measurement device 182 maybe mounted to a placement device 400, to which is mounted an orthopedictrial 410 (e.g., a tibial trial plate) or a final orthopedic implant. Itshould be noted that while the following example is described withrespect to a tibial trail 410, any orthopedic trial or final implant forany joint (e.g., knee, hip, shoulder, ankle, etc.) may be similarly usedin conjunction with the placement device 400.

In exemplary form, the placement device 400 has known dimensions and mayaccept the second inertial measurement device 182 in only a singleorientation and position. As a result, the when the second inertialmeasurement device 182 is mounted to the placement device 400, the imageguided surgical system 100 may realize this mounting automatically orrely on a manual input to tell the system that the second inertialmeasurement device is now mounted to the placement device. Either way,the image guided surgical system 100 uses the registration position andorientation of the second inertial measurement device 182 (when it wasmounted to the cutting guide 190) to calculate the position andorientation of the IMU 183 in real-time. Because the position andorientation of the IMU 183 with respect to the second inertialmeasurement device 182 is constant, and the second inertial measurementdevice can only be mounted to the placement device 400 in a singleposition and orientation, by calculating the position and orientation ofthe IMU, the image guided surgical system 100 is operative to calculatethe position and orientation of the placement device 400.

In this exemplary embodiment, the placement device 400 may only bemounted to the orthopedic trial or final implant in a predeterminedposition and orientation, where the image guided surgical system 100includes CAD files or similar data for each orthopedic trial or finalimplant that may be utilized during the TKA procedure. In this manner,the image guided surgical system 100, by knowing the position andorientation of the placement device, and knowing which orthopedic trialor implant is mounted to the placement device (whether automatically orvia manual input), calculates the relative position of the orthopedictrial or implant with respect to the patient bone (e.g., tibia). As aresult, the surgeon may be guided as to the position and orientation ofthe orthopedic trial or implant in accordance with a pre-operativesurgical plan. By guiding the surgeon concerning placement andorientation of the final implant and/or orthopedic trail, the surgeon isable to more precisely position and orient the implant/trial. If theimplant/trial does not appear to confirm, the surgeon may makeprofessional judgments concerning whether further bone cuts arenecessary, whether a different size implant/trail is necessary, andwhether a different implant altogether is necessary.

With reference to FIG. 42, it is also within the scope of the disclosureto remove the second inertial measurement device 182 from the cuttingguide 190 (or other surgical device it is mounted to) and mount theinertial measurement device to a tensioning device 420 (while retainingthe rigid reference 170 mounted to a patient bone). In this exemplarycircumstance, the tensioning device 420 may comprise a wirelesstensioner or load measurement device. By way of example, the loadmeasurement device 420 may comprise a multitude of piezoresistive,capacitive, and/or piezoelectric based strain sensors. These sensors maybe configured into an array of sensors for mapping the location of highstrain on the joint surface. In exemplary form, the load measurementdevice 420 may have a surface that can be flat or surfaced to match thearticulating surface of the joint component. Moreover, the loadmeasurement device 420 may include a microcomputer and/or a wirelesstransmitter for data communication.

In exemplary form, the load measurement device 420, in the context ofTKA, may be placed after the femoral and tibia resection to evaluate thetightness of the joint. As part of evaluating the tightness of thejoint, the joint may be taken through a range of motion while anorthopedic trial or the final implant is in place. More specifically,when teamed with IMU data, the load measurement device 420 may providejoint tightness information along with the flexion angles calculatedfrom IMU data, not to mention the overall position and orientation ofthe device using the IMU data.

In exemplary form, the load measurement device 420 has known dimensionsand may accept the second inertial measurement device 182 in only asingle orientation and position. As a result, the when the secondinertial measurement device 182 is mounted to the load measurementdevice 420, the image guided surgical system 100 may realize thismounting automatically or rely on a manual input to tell the system thatthe second inertial measurement device is now mounted to the loadmeasurement device. Either way, the image guided surgical system 100uses the registration position and orientation of the second inertialmeasurement device 182 (when it was mounted to the cutting guide 190) tocalculate the position and orientation of the IMU 183 in real-time.Because the position and orientation of the IMU 183 with respect to thesecond inertial measurement device 182 is constant, and the secondinertial measurement device can only be mounted to the load measurementdevice 420 in a single position and orientation, by calculating theposition and orientation of the IMU, the image guided surgical system100 is operative to calculate the position and orientation of the loadmeasurement device 420.

In this exemplary embodiment, the image guided surgical system 100, byknowing the position and orientation of the IMU 182, calculates therelative position of the load measurement device 420 with respect to thepatient bone (e.g., tibia). As a result, the surgeon may receivefeedback from the load measurement device 420 indicative of whether thejoint loading is or is not consistent with a pre-operative surgicalplan. By guiding the surgeon concerning joint tightness, the surgeon isable address any concerns by professional judgments concerning whetherfurther bone cuts are necessary, whether a different size implant/trailis necessary, and whether a different implant altogether is necessary.

By way of summary, the exemplary disclosed steps for carrying out a TKAreplacement or revision surgery may include one or more of thefollowing, without limitation, in any order: (a) mount PAM 130 to femur160; (b) mount reference IMU 173 to femur 160; (c) mount instrument IMU183 to cutting guide 190; (d) register IMUs 173, 183 with respect to oneanother, where at least one IMU is in a known position with respect tothe patient bone 160; (e) reposition the cutting guide 190 with respectto the PAM 130 (femur specific) (that may include repositioning therevolute joints 222, 234 and spherical joint 236) using IMU guidance toposition the cutting slot 200 to guide a distal femoral resection cutconsistent with a pre-operative surgical plan; (f) make the distalfemoral resection cut; (g) reposition the cutting guide 190 with respectto the PAM 130 (tibia specific) (that may include repositioning therevolute joints 222, 234 and spherical joint 236) using IMU guidance toposition the cutting slot 200 to guide a proximal tibial resection cutconsistent with a pre-operative surgical plan; (h) make the proximaltibial resection cut; (i) perform evaluation(s) with guided IMU loadmeasurement device to determine any needed resection alterations andappropriate component rotation; (j) using IMU guidance and usingdisplay(s) to show user real-time or near real-time updates on pinpositions, posterior resections, anterior notching, internal/externalrotation, (1) reposition the cutting guide to 4-in-1 pin position, (2)unlock lower revolute joint, rotate until desired pin proximity isachievable, (3) lock bottom revolute joint, unlock spherical joint andreposition until desired pin position is achievable, (4) lock all jointswhen acceptable position achieved, (5) drill surgical pin holes, (6)mount surgical pins to resected femur using the drilled holes; (k)remove PAM 130, mechanical connections 220, and cutting guide 190; (l)mount a multi-cut cutting guide to the resected distal femur using thesurgical pins as guides; (m) mount a guide foot 260 to the resecteddistal femur using the surgical pins as guides, where the guide foot isultimately mounted to a repositionable cutting guide 190; (n) adjust cutslot for each of posterior, posterior chamfer, anterior chamfer andanterior cuts on the distal femur; (o) make each of each of posterior,posterior chamfer, anterior chamfer and anterior cuts on the distalfemur (that may include using a surgical saw); (p) position orthopedictrial components on the resected femur and tibia to verify componentsize and placement position; (q) place final orthopedic components onthe resected femur and tibia.

Referring to FIG. 43, it is also within the scope of the instantdisclosure to provide a kit 500 that includes one or more of thecomponents disclosed herein, in addition to final orthopedic implants(and optionally trial orthopedic implants). Given the need forinstrument and inventory reduction in orthopedic surgery, specificallyin primary knee arthroplasty, it is desirable that the kit 500 bedeliverable in a “just-in-time” or made-to-order manner to reduce neededshelf space at healthcare facilities and instrument/inventory costs forimplant manufacturers. Each component of the kit 500 may be deliveredsterile or non-sterile depending on customer requirements.

As part of an exemplary kit 500, the kit may include anon-patient-specific package 510 comprising one or more of thefollowing: two or more IMU devices 172, 182, a rigid reference housing174, the mechanical connections 220, the cutting guide 190, the guidefoot 260, a placement device 400, and a tensioning device 420. Theforegoing exemplary package 510 components of the kit 500 areanticipated to be single use (i.e., disposable), but could also bere-sterilized and reused as multi-use components. In this fashion, thekit 500 may or may not include the non-patient-specific package 510,particularly where a surgeon is reusing components from a prior kit. Inaddition to non-patient-specific components, the kit 500 may includevarious patient-specific components.

By way of example, the kit 500 may include a patient-specific package520 comprising one or more of the following: a distal femur PAM 130, aproximal tibia PAM 130, patient-specific orthopedic implants andoptionally orthopedic trials (e.g., femoral component, tibial tray,tibial tray insert, etc.). The foregoing exemplary package 520components of the kit 500 are anticipated to be used for only a singlesurgical procedure (i.e., disposable).

By way of further example, the kit 500 may include an optional package530 including components that a surgeon or hospital may anticipate usingas part of the surgical procedure, whether or not the components aresingle use or reusable. In exemplary form, the optional package 530 mayinclude one or more of the following: surgical pins, surgical drillbit(s), static multi-cut bone cutting guide (e.g., 4-in-1 cutting block300), reconfigurable multi-cut bone cutting guide without navigation,and non-patient-specific orthopedic implants and optionally orthopedictrials (e.g., femoral component, tibial tray, tibial tray insert, etc.).The foregoing exemplary package 530 components of the kit 500 areanticipated to be single use (i.e., disposable), but could also bere-sterilized and reused as multi-use components.

By way of even further example, the kit 500 may include one or more ofthe packages 510, 520, 530 and, when including a patient-specificpackage 520, may be manufactured and delivered in a just-in-timefashion. Moreover, as part of the kit, before or at the time of surgery,a surgical plan may be prepared and made available to the surgicalnavigation software 104, wirelessly or via USB or similar portablememory, and used with the kit 500 components to execute the desiredsurgical procedure such as, without limitation, TKA.

Following from the above description, it should be apparent to those ofordinary skill in the art that, while the methods and apparatuses hereindescribed constitute exemplary embodiments of the present invention, theinvention described herein is not limited to any precise embodiment andthat changes may be made to such embodiments without departing from thescope of the invention as defined by the claims. Additionally, it is tobe understood that the invention is defined by the claims and it is notintended that any limitations or elements describing the exemplaryembodiments set forth herein are to be incorporated into theinterpretation of any claim element unless such limitation or element isexplicitly stated. Likewise, it is to be understood that it is notnecessary to meet any or all of the identified advantages or objects ofthe invention disclosed herein in order to fall within the scope of anyclaims, since the invention is defined by the claims and since inherentand/or unforeseen advantages of the present invention may exist eventhough they may not have been explicitly discussed herein.

What is claimed is: 1-54. (canceled)
 55. A surgical equipment kit for aknee replacement or revision procedure comprising: a first inertialmeasurement unit (IMU) having a gyroscope, an accelerometer, and amagnetometer; a second inertial measurement unit (IMU) having agyroscope, an accelerometer, and a magnetometer; a tibialpatient-specific anatomical mapper (PAM) that includes a surfaceprecisely and correctly mating with a tibial surface in only a singlelocation and orientation, where the tibial PAM is configured to bemounted to the tibial surface; a femoral patient-specific anatomicalmapper (PAM) that includes a surface precisely and correctly mating witha femoral surface in only a single location and orientation, where thefemoral PAM is configured to be mounted to the femoral surface; acutting guide configured to be repositionably coupled to at least one ofthe tibial PAM and the femoral PAM, the cutting guide including at leastone of a cutting slot and a pin orifice, the guide configured to coupleto the first IMU in a predetermined known position and orientation; anda mechanical connection comprising at least two joints to operativelycouple the cutting guide to at least one of the tibial PAM and thefemoral PAM; wherein the second IMU is configured to be operativelycoupled to at least one of the tibial PAM and the femoral PAM.
 56. Thekit of claim 55, wherein the at least two joints comprise at least oneof a revolute joint and a spherical joint.
 57. The kit of claim 55,wherein the at least two joints comprise a pair of revolute joints and aspherical joint.
 58. The kit of claim 55, further comprising anorthopedic implant configured to replace at least a portion of a kneejoint.
 59. The kit of claim 58, wherein the orthopedic implant comprisesa patient-specific implant.
 60. The kit of claim 59, wherein thepatient-specific implant includes a femoral condyle and a tibial trayinsert.
 61. The kit of claim 59, wherein the patient-specific implantincludes a femoral implant having a pair of condyles and a tibial trayinsert having a pair of condyle receivers.
 62. The kit of claim 58,wherein the orthopedic implant comprises a mass customized implant. 63.The kit of claim 62, wherein the mass customized implant includes afemoral condyle and a tibial tray insert.
 64. The kit of claim 62,wherein the mass customized implant includes a femoral implant having apair of condyles and a tibial tray insert having a pair of condylereceivers.
 65. The kit of claim 58, wherein the orthopedic implantcomprises a non-patient-specific implant.
 66. The kit of claim 65,wherein the non-patient-specific implant includes a femoral condyle anda tibial tray insert.
 67. The kit of claim 65, wherein thenon-patient-specific implant includes a femoral implant having a pair ofcondyles and a tibial tray insert having a pair of condyle receivers.68. The kit of claim 55, further comprising a reference housingconfigured to be rigidly mounted to at least one of a tibia and a femur,the reference housing configured to mount to the first IMU correctly inonly a single position and orientation.
 69. The kit of claim 55, furthercomprising a 4-in-1 static cutting block.
 70. The kit of claim 55,further comprising a 4-in-1 reconfigurable cutting block.
 71. The kit ofclaim 55, further comprising a physical memory device upon which isstored computer readable code that, when executed by a computer, isoperative to provide surgical navigation guidance consistent with apre-operative plan.
 72. The kit of claim 55, further comprising a copyof an internet address that may be accessed to provide stored computerreadable code that, when executed by a computer, is operative to providesurgical navigation guidance consistent with a pre-operative plan.73-127. (canceled)